Second step: Using the joke as a running gag.

The second step to making a running gag.

Now you need to use this joke in other situations where it is still funny.

Let us use on of the examples from the first lesson.

We'll use the one with the British lady.

You could make it where everyone that meets her to where every time she meets somebody they ask her if she is British.

She would most likely get tired of it after a while and become snippy saying things like "No I just talk like this because everyone thinks it's bloody hilarious!". 

For a joke to be considered a running gag you must use it enough that people expect it but not to the point that you overuse it.